Harvest time for fennel varies, depending on which part of the plant is to be used. Leaves may be picked as needed, and seeds should be gathered when the seed heads begin to turn brown, but before they are completely brown.
The fennel plant grows up to 5 feet in height, and has feather-like leaves, and a large bulb end. Hot, dry climates are ideal for the sun-loving plant, but it will tolerate almost any garden condition.
Fennel is a tall plant, and may need to be staked for support if not protected from wind. Fennel may also inhibit the growth of other plants, so consider placing it away from other vegetation.